JP2012254841A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of locating a sheet reversing conveyance part below a sheet cooling part without damaging the cooling effect of the sheet cooling part.SOLUTION: A sheet P sent from the sheet cooling part 50 is U-turned downward in a conveyance direction through a U-shaped conveyance guide member 61, and conveyed and guided to the reversing conveyance part 60 which is located below the sheet cooling part 50. The sheet P is reversed through a U-shaped reversing guide member 63 of the reversing conveyance part 60, and sent to a main conveyance part 40 at the upstream position from an image forming unit 10.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a fax machine, and the like, and a multifunction machine.

  In image forming apparatuses such as copying machines and printers, cooling of a sheet immediately after image formation is mainly performed by cooling with a fan. However, in a model with a high linear speed such as a high-speed production printer, the paper temperature cannot be effectively reduced by cooling with fan air blowing. Therefore, as shown in Patent Document 1, a fixing unit is used by a contact type cooling device. The paper heated in is actively cooled.

JP 2008-112102 A

  The image forming apparatus described above can form an image on both sides of a sheet as well as an image on one side of the sheet. In a scene such as double-sided printing, the sheet is formed after the image is formed on the sheet surface. The front and back are reversed.

  As shown in Japanese Patent Application Laid-Open No. 2004-133867, the paper is reversed by a paper reversing mechanism provided on the downstream side of the paper cooling unit.

  In order to reduce the size of the image forming apparatus, it is conceivable to arrange a sheet reversing mechanism below the sheet cooling unit. In this case, however, a sheet with a high printing rate has a high heat retention on the image surface even after cooling. For this reason, the heat on the surface of the paper that is turned upside down by the paper turning mechanism may affect the cooling effect of the paper cooling unit.

  Therefore, the present invention provides an image forming apparatus in which the reverse conveyance section of the sheet can be arranged below the sheet cooling section without impairing the cooling effect of the sheet cooling section.

  The image forming apparatus of the present invention can form images on both sides of a sheet. The image forming apparatus includes a main transport unit that transports paper along a main transport path, an image forming unit that forms an image on the paper transported by the main transport unit, and an image formed by the image forming unit. A sheet cooling unit that cools the sheet, and a reversal conveyance unit that conveys the sheet along the reversal conveyance path and reverses the front and back of the sheet are provided.

  The reverse conveying unit is disposed below the sheet cooling unit, and the sheet fed from the sheet cooling unit is conveyed and guided to the reverse conveying unit by a U-shaped conveyance guide member. Main features.

  According to the present invention, since the reverse conveying unit is arranged below the sheet cooling unit, the image forming apparatus can be downsized.

  Then, the sheet fed from the sheet cooling unit is conveyed and guided to the reverse conveyance unit by the U-shaped conveyance guide member, so that the image surface of the sheet can face downward on the side opposite to the sheet cooling unit. As a result, the heat retained on the image surface of the sheet can be prevented from being radiated to the sheet cooling unit, and the cooling effect of the sheet cooling unit can be avoided.

1 is an overall configuration diagram conceptually showing an image forming apparatus of the present invention. The typical explanatory view showing the important section of the 1st embodiment of the present invention. The typical explanatory view showing the important section of a 2nd embodiment of the present invention. FIG. Explanatory drawing which shows the reverse conveyance pattern of the paper in 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An image forming apparatus 1 shown in FIG. 1 is an electrophotographic image forming apparatus such as a copying machine, for example, and arranges a plurality of photoconductors facing a single intermediate transfer belt in a vertical direction to form a full color image. This is a so-called tandem color image forming apparatus.

  In the present embodiment, the image forming apparatus 1 includes a first main body 1A disposed in the center, a second main body 1B disposed on the left side of the first main body 1A in FIG. 1, and a paper feed disposed on the right side of the first main body 1A. 1C.

The image forming apparatus 1 mainly includes a document reading device 2, an image forming unit 10, a fixing device 30, a main conveyance unit 40, a sheet cooling unit 50, and a reverse conveyance unit 60.

In the present embodiment, the image forming unit 10 is disposed in the main body 1A, and the fixing device 30 is disposed in the second main body 1B together with the paper cooling unit 50 and the reverse conveying unit 60. You may make it arrange | position to the main body 1A.

  The document reader 2 has an unillustrated automatic document feeder provided at the top of the first main body 1A, and obtains an image signal by reading an image of the document while conveying the document.

  Specifically, the document reading device 2 irradiates an image of the document with a lamp and forms an image of the reflected light on the light receiving surface of the image sensor. The image sensor photoelectrically converts the incident light and outputs a predetermined image signal to the image reading control unit 3. The image reading control unit 3 performs processing such as A / D conversion, shading correction, and compression on the image signal, and outputs it as image data to a main control unit (not shown). Note that the image data input to the main control unit is not limited to the data read by the document reading device 2, for example, the data received from a personal computer connected to the image forming device 1 or another image forming device. May be.

  The image forming unit 10 creates a toner image based on the image data, and transfers the created toner image onto the paper P. The image forming unit 10 is mainly composed of exposure units 15Y, 15M, 15C, and 15K, charging / developing units 20Y, 20M, 20C, and 20K, an intermediate transfer unit 23, and a secondary transfer roller 26.

  Each of the exposure units 15Y to 15K includes a laser light source, a polygon mirror, a plurality of lenses, and the like. Each of the exposure units 15Y to 15K scans and exposes the surfaces of photosensitive drums 21Y, 21M, 21C, and 21K, which will be described later, with a laser beam in accordance with output information output from the main control unit based on image data. . By this scanning exposure, latent images are formed on the photosensitive drums 21Y to 21K.

  The charging / developing unit 20Y mainly includes a photosensitive drum 21Y that rotates about a rotation axis and a charging / developing unit 22Y that is disposed around the photosensitive drum 21Y. The toner image corresponding to yellow is transferred to the photosensitive drum. It is formed on 21Y. The other charging / developing units 20M, 20C, and 20K have the same configuration as the charging / developing unit 20Y, and charging / developing units 22M, 22C, and 22K are provided around the photosensitive drums 21M, 21C, and 21K, respectively. The toner images corresponding to magenta, cyan, and black are formed on the photosensitive drums 21M, 21C, and 21K, respectively.

  Specifically, the surfaces of the photosensitive drums 21Y to 21K are uniformly charged by the charging / developing units 22Y to 22K, and as described above, latent images are formed on the surfaces of the exposing units 15Y to 15K. Is done.

  The charging / developing units 22Y to 22K develop latent images on the photosensitive drums 21Y to 21K by developing with toner.

  As a result, toner images are formed on the respective photosensitive drums 21Y to 21K. The toner images formed on the individual photosensitive drums 21 </ b> Y to 21 </ b> K are sequentially transferred to predetermined positions on the intermediate transfer belt 24 constituting the intermediate transfer unit 23.

  The secondary transfer roller 26 transfers the toner image transferred onto the intermediate transfer belt 24 onto the paper P conveyed at a predetermined timing by the main conveyance unit 40.

  The paper P on which the toner image is transferred, that is, the paper P having an unfixed toner image is sent to the fixing device 30.

  The fixing device 30 presses and heats the paper P to fix the toner image on the paper P. The fixing device 30 is mainly composed of an upper fixing roller 31 and a lower fixing roller 32, for example. The upper fixing roller 31 and the lower fixing roller 32 are arranged in pressure contact with each other, and a fixing nip portion is formed between the upper fixing roller 31 and the lower fixing roller 32. Further, a heater (not shown) is built in the fixing upper roller 31 as a heating unit for performing heat fixing, and the fixing upper roller 31 is heated by radiant heat from the heater.

  In the fixing device 30, the sheet P is conveyed in such a manner that the surface to be fixed (the surface including the unfixed toner image) faces the fixing upper roller 31, and passes through the fixing nip portion in the conveyance process. As a result, the toner image is fixed onto the paper P through the pressure applied by the upper fixing roller 31 and the lower fixing roller 32 and the heat action of the upper fixing roller 31.

  In the present embodiment, the image forming unit 10 and the fixing device 30 described above function as an image forming unit.

  That is, the image forming unit (1) charges the photosensitive drums 21Y to 21K. (2) The exposure units 15Y to 15K form electrostatic latent images on the photosensitive drums 21Y to 21K. (4) The toner image on the photoconductive drums 21Y to 21K is primarily transferred to the intermediate transfer belt 24. (5) The toner image on the intermediate transfer belt 24 is transferred to the sheet P two times. The toner image is formed on the paper P conveyed by the main conveyance unit 40 described later through a series of processes of (6) fixing the toner image on the paper P to be transferred next.

The main transport unit 40 includes a guide member and a plurality of rollers, and is arranged along a predetermined transport path (hereinafter referred to as a main transport path) defined for forming an image on the paper P. The main transport unit 40 is configured to extend from the first main body 1A to the second main body 1B. From the paper feed tray Tr ₁ of the first main body 1A or the paper feed trays Tr _{2 to} Tr ₄ of the paper feed unit 1C. When the paper P is supplied, the paper P is transported along the main transport path. The sheet conveyance direction FD1 by the main conveyance unit 40 corresponds to a direction (sub-scanning direction) orthogonal to the main scanning direction of the toner image on the sheet P.

  The main transport unit 40 supplies the paper P to the image forming position by the image forming unit in the process of transporting the paper P along the main transport path. Specifically, the paper P is supplied to a secondary transfer position where the toner image is transferred onto the paper P by the transport roller 41 and the registration roller 45, and the toner image is fixed on the paper P by the transport roller 42. 30.

  The paper P that has passed the secondary transfer position and the fixing position, which are image forming positions, is conveyed to a paper cooling unit 50 described later. The paper P cooled by the paper cooling unit 50 is guided by the guide member, and is discharged by the discharge roller 46 to the paper discharge tray 47 attached to the outer side surface of the casing of the second main body 1B.

  On the other hand, when the toner image is formed not only on the front side of the paper but also on the back side of the paper, the main transport unit 40 transports the paper P that has undergone image forming processing and cooling on the front surface of the paper to the reverse transport unit 60. .

  As will be described later, the reversing conveyance unit 60 includes a guide member and a plurality of rollers, and is arranged along a predetermined conveyance path (hereinafter referred to as a reversal conveyance path) defined for reversing the front and back of the paper P. Yes. When the reverse conveyance unit 60 receives the paper P from the main conveyance unit 40 on the downstream side of the paper cooling unit 50, the reverse conveyance unit 60 conveys the paper P along the reverse conveyance path.

  The paper P that has been turned upside down by the reversing conveyance unit 60 and sent to the refeed conveyance path 70 is reconveyed to the image forming unit by the conveyance rollers 43 and 44.

  FIG. 2 schematically shows the configuration of the paper cooling unit 50 and the reverse conveyance unit 60 described above.

  The sheet cooling unit 50 includes a pair of upper and lower belt units 51 and 52. The sheet P sent out from the fixing device 30 is sandwiched between the belt units 51 and 52 and brought into close contact with the endless belts 53 and 54. It is transported along the main transport path of the unit 40.

  At least one of the belt units 51 and 52, for example, the inner side of the upper belt unit 51, a cooler, for example, a heat sink 55, which is in sliding contact with the back surface of the endless belt 53 is disposed. As a result, the sheet P heated by the fixing device 30 is cooled while being sandwiched and conveyed by the belt units 51 and 52.

  In order to effectively perform the heat radiating action of the heat sink 55, cooling air is positively introduced into the endless belt 53 from one side by the cooling fan 56 (see FIG. 4).

  The reversing conveyance unit 60 is arranged below the sheet cooling unit 50, and includes an upper first conveyance unit 60A and a lower second conveyance unit 60B arranged in multiple stages in the vertical direction. Yes.

  60 A of 1st conveyance parts carry out U-turn of the paper P sent out from the paper cooling part 50 as shown by arrow FD2, and convey the said paper P to the lower side of the paper cooling part 50.

  The second transport unit 60B reverses the paper P sent out from the first transport unit 60A in the transport direction indicated by the arrow FD2, and transports and guides the paper P to the lower side of the first transport unit 60A. 2 The sheet P, whose front and back sides are reversed, is sent to the main transport unit 40 at a position upstream from the image forming unit via the transport unit. That is, in the example shown in FIG. 1, the paper P is sent from the second transport unit 60 </ b> B to the refeed transport path 70, and the paper P is positioned upstream of the secondary transfer roller 26 via the refeed transport path 70. To the registration roller 45.

  The reversing conveyance unit 60 of the first embodiment shown in FIGS. 1 and 2 receives the paper P sent out from the first conveyance unit 60A by the second conveyance unit 60B and switches it back to the main conveyance unit 40. A switchback reversing mechanism is provided.

  Specifically, the first transport unit 60A receives the paper P sent out from the paper cooling unit 50, makes a U-turn downward, and bends in a U shape that guides the conveyance to the lower vicinity of the paper cooling unit 50. The conveyance guide member 61 and the flat upper guide member 62 that is connected to the U-shaped conveyance guide member 61 and is disposed below the sheet cooling unit 50. Each of the conveyance guide member 61 and the upper guide member 62 includes conveyance rollers 61a and 62a.

  The second transport unit 60B includes a reverse guide member 63 bent in a U-shape that reverses the paper P sent from the first transport unit 60A in the transport direction FD2 and transports the paper P to the lower side of the upper guide member 62. And a flat lower guide member 64 which is disposed below the upper guide member 62 and temporarily receives the paper P sent out from the reversing guide member 63, switches it back and sends it to the refeed conveyance path 70. is doing. That is, the reverse guide member 63 and the lower guide member 64 constitute a switchback type reverse mechanism. Both the reverse guide member 63 and the lower guide member 64 include transport rollers 63a and 64a.

  Thus, the sheet P cooled and sent out by the sheet cooling unit 50 is U-turned downward by the conveyance guide member 61 and is conveyed and guided to the upper guide member 62 with the surface on which the image is formed facing downward. The paper P sent out from the upper guide member 62 is reversed by the reverse guide member 63 and is conveyed and guided to the lower guide member 64 with the surface facing upward. Once the paper P is received by the lower guide member 64, it is switched back and sent out to the refeed conveyance path 70 in a reversed state with the surface facing upward. Therefore, the lower guide member 64 is the post-paper reversal position.

  According to the image forming apparatus 1 of the present embodiment having the above-described configuration, the reverse conveying unit 60 including the upper first conveying unit 60A and the lower second conveying unit 60B arranged in multiple stages in the vertical direction is replaced with the sheet cooling unit. 50, the second main body 1B can be downsized, and the image forming apparatus 1 can be configured to be compact as a whole.

  Then, the sheet P sent out from the sheet cooling unit 50 is U-turned downward and guided by the U-shaped conveyance guide member 61 in the first conveyance unit 60A. The surface can face downward on the side opposite to the sheet cooling unit 50. As a result, it is possible to suppress the heat retained on the image surface of the paper P from being radiated to the paper cooling unit 50 and to prevent the cooling effect of the paper cooling unit 50 from being hindered.

  In the present embodiment, the reverse conveying unit 60 includes a U-shaped reverse guide member 63 and a lower guide member 64 in the lower second transport unit 60B to form a switchback reverse mechanism. Since the switchback method is adopted, the configuration can be simplified.

  Here, the paper P sent out from the paper cooling section 50 is temporarily received by the upper guide member 62 in the upper first transport section 60A, switched back by the upper guide member 62, and transported to the second transport section 60B. The sheet P can be reversed and sent to the main transport unit 40 by the second transport unit 60B. However, when the sheet P is switched back in the upper first transport unit 60A in this way, the residence time of the paper in the first transport unit 60A becomes longer.

  On the other hand, in the present embodiment, in the upper first conveyance unit 60A, when the U-shaped conveyance guide member 61 causes the paper P feed direction to be U-turned downward, the upper guide member 62 causes the image surface of the paper P to face downward. Then, it is passed as it is, sent out to the lower second conveying section 60B, and switched back by the reverse guide member 63 and the lower guide member 64. For this reason, the residence time of the paper P in the upper first transport unit 60A can be shortened, and the thermal influence on the paper cooling unit 50 can be more effectively avoided.

  3 and 4 show a second embodiment of the present invention. In this embodiment, as shown in FIG. 5, the feeding direction FD2a of the sheet P of the transport guide member 61 in the first transport section 60A and The reversing direction FD2b of the paper P by the reversing guide member 63 in the second transport unit 60B is orthogonal, and the front and back are reversed via the first and second transport units 60A and 60B and enter the image forming unit. The same edge method is adopted in which the ends of the paper P are the same on the front and back.

  Specifically, the first transport unit 60A in the upper stage receives the paper P sent out from the paper cooling unit 50, makes a U-turn downward, and guides the conveyance to the lower vicinity of the paper cooling unit 50 described above. A first guide member 61 bent in a letter shape and a flat upper guide member 65 disposed below the sheet cooling unit 50 are configured. The upper guide member 65 transports the paper P in the paper feed direction FD2a of the transport guide member 61, and feeds the paper P from the upper guide member 65 in a direction orthogonal to the paper feed direction FD2a of the transport guide member 61. A conveyance roller 65b. These transport rollers 65a and 65b are switched in operation when the paper P is received and when it is sent out.

  The lower second conveyance unit 60B reverses the sheet P sent out from the upper first conveyance unit 60A downward in a direction FD2b perpendicular to the feeding direction FD2a of the conveyance guide member 61, and lowers the upper guide member 65. The reversing guide member 63 bent in the above-mentioned U shape for conveying and guiding to the upper side, and the flat lower guide member 66 disposed below the upper guide member 65. The lower guide member 66 feeds the paper in the paper feed direction FD2b of the reverse guide member 63, and feeds the paper P from the lower guide member 66 in the same direction as the paper feed direction FD2a of the above-described transport guide member 61. A conveyance roller 66a. That is, the reversing guide member 63 and the lower guide member 66 constitute a same edge type reversing mechanism. The transport rollers 66a and 66b are switched between when the paper P is received and when it is delivered.

  As a result, the sheet P cooled and sent out by the sheet cooling unit 50 is U-turned downward by the U-shaped conveyance guide member 61 and conveyed to the upper guide member 65 with the surface on which the image is formed facing downward. Is done.

  FIG. 5 shows a conveyance pattern of the paper P. In the first conveyance unit 60A, the paper P is conveyed and guided along the feeding direction FD2a from the conveyance guide member 61 to the upper guide member 65.

  The paper P delivered from the upper guide member 65 is inverted downward in a direction FD2b orthogonal to the paper delivery direction FD2a of the transport guide member 61 by the reverse guide member 63 of the second transport unit 60B. Then, in the reverse state in which the surface of the paper P is directed upward by the lower guide member 65, the same end as that when the paper P has entered the reverse transport unit 60 is used as the leading end to the re-feed transport path 70. Send it out. Accordingly, the lower guide member 65 is the post-paper reversal position.

  According to the image forming apparatus 1 of the second embodiment, similarly to the first embodiment, it is possible to avoid the thermal influence on the sheet cooling unit 50 due to the heat retained on the image surface of the sheet P, and by adopting the same edge inversion method. Thus, the alignment accuracy of the front and back images of the paper P can be increased.

  That is, in the reverse conveyance unit 60, the paper P is reversely conveyed via a conveyance path in which the conveyance direction FD2a and the reverse direction FD2b are orthogonal to each other, and the leading and trailing edges of the paper P entering the image forming position on the paper surface Can be reversed without switching. As a result, when forming the front and back images, it is possible to form an image based on the same end portion of the paper P, and the alignment accuracy of the front and back images of the paper P is improved.

  Here, in the present embodiment, as shown in FIG. 4, the arrangement position of the reversing guide member 63 is the cooling air introduced side of the cooling fan 56 in the paper cooling unit 50, that is, the cooling introduced into the heat sink 55. It is set upstream of the industrial air flow.

  Accordingly, it is possible to avoid the sheet P reversed by the reversing guide member 63 from being affected by the exhaust heat of the cooling air heat exchanged by the heat sink 55.

  In the above embodiment, the type in which the image forming apparatus 1 is divided into the first main body 1A, the second main body 1B, and the paper feeding unit 1C is illustrated for convenience, but each functional member is arranged in a single casing. Of course, it may be provided.

  Further, although the paper cooling unit 50 is exemplified using the heat sink 55, a heat pipe or a Peltier element can also be used as a cooler.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 10 ... Image forming unit (image forming part)
30. Fixing device (image forming unit)
40 ... main transport unit 50 ... paper cooling unit 51/52 ... belt unit 53/54 ... endless belt 55 ... cooler 56 ... cooling fan 60 ... reverse transport unit 60A ... first transport unit 60B ... second transport unit 61 ... U Character-shaped conveyance guide member 63... U-shaped reversal guide member 70.

Claims (5)

In an image forming apparatus capable of forming images on both sides of paper,
A main transport section for transporting paper along the main transport path;
An image forming unit that forms an image on a sheet conveyed by the main conveying unit;
A paper cooling unit for cooling the paper on which an image is formed by the image forming unit;
A reversal transport unit that transports the paper along the reverse transport path and reverses the front and back of the paper,
The reverse conveyance unit is disposed below the paper cooling unit, and the paper fed from the paper cooling unit is conveyed and guided to the reverse conveyance unit by a U-shaped conveyance guide member. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the U-shaped conveyance guide member is configured to send the sheet to the reversal conveyance unit so that an image surface thereof faces downward.   2. The reverse conveying section includes a switchback type reversing mechanism that reverses the sheet by a U-shaped reversing guide member, switches it back, and sends it to the main conveying section. Or the image forming apparatus according to 2;   The reversing conveyance unit reverses the edge of the same edge type by reversing the sheet in a direction perpendicular to the sheet feeding direction of the U-shaped conveyance guide member by a U-shaped reversing guide member and feeding it to the main conveying unit. The image forming apparatus according to claim 1, further comprising a mechanism. The sheet cooling unit includes a pair of endless belts that convey the sheet therebetween,
A cooler disposed in sliding contact with the inside of at least one endless belt;
A cooling fan that introduces cooling air from one side to the inside of the one endless belt,
The image forming apparatus according to claim 4, wherein an arrangement position of the U-shaped reversing guide member is set on a cooling air introduction side of the sheet cooling unit.

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